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The Kola Superdeep Borehole in the Pechengsky District, Kola Peninsula, Russia, the result of a Soviet scientific drilling project between 1970 and 2005. The deepest borehole, named SG-3, reached in 1989 is 40,230 ft (12,262 metres) deep.

The drilling was stopped in 1992 due to higher-than-expected temperatures (180 °C/356 °F instead of 100 °C/212 °F). The project was closed in 2005 because of lack of funding. All of the equipment was scrapped and the site is abandoned since 2008.

The world's deepest mine, the TauTona gold mine in Carletonville, South Africa with its maximum depth of 2.4 mi (3.9 km), reached in 2008.

The KTB super deep borehole, the result of the German Continental Deep Drilling Program near Windischeschenbach, Germany. The 9,101 m (29859 ft or 5.655 mi) deep hole was drilled between 1990 and 1994, and the temperature was more than 500 °F (260 °C) down there.

The Door To Hell, or Darvaza, in the middle of the Karakum Desert, Turkmenistan

A drilling rig was set up here by Soviet geologists in 1971 and started operations, but the ground collapsed into a wide crater and the rig disappeared. A huge amount of methane gases was released, so the scientists decided to burn it off. They thought it would only take a few days, but the methane has been burning since then.

The Berkeley Pit, a former open pit copper mine in Butte, Montana. It's filled to a depth of 900 ft (270m) with acidic water and contains some dangerous chemicals like arsenic, sulfuric acid and cadmium, among others.

The Big Hole (or the Kimberley Diamond Mine) in Kimberley, South Africa, excavated by hand between 1871 and 1914. It has a surface of 17 hectares (42 acres) and a width of 1519 ft (463 m). It had a depth of 787 ft (240 m), but partially infilled with debris, so it's 705 ft (215 m) deep now.

The Mir mine, a former diamond mine (1957-2011) in Mirny, Eastern Siberia, Russia. The airspace above the 1,722 ft (525 m) deep pit is closed for helicopter because some of them were sucked in by the air flow.

The deepest hand-dug well in the world, in Woodingdean, East Sussex, England.

Bonus: The Sudbury Neutrino Observatory, the world's deepest physics laboratory, 6,800 feet (2,07 km) underground in the still operating Creighton Mine, Sudbury, Ontario, Canada. It was used between 1999 and 2006 to detect solar neutrinos through their interactions with a tank of heavy water.